This disclosure relates to novel red electrochromic materials and electrochromic devices using the same. This disclosure also relates to novel electrochromic materials in which fluorene or carbazole groups are bonded to a viologen moiety to produce a red color, and electrochromic devices comprising the electrochromic materials.
Electrochromism is a phenomenon in which the color of a material reversibly changes depending on the direction of an electric field when a voltage is applied to the material. Electrochromic materials refer to materials that exhibit electrochromism and can undergo reversible changes in optical properties by electrochemical redox reactions. That is, some electrochromic materials exhibit their characteristic color when no external electric field is applied and then show different colors in the presence of an electric field. Contrary to this, some other electrochromic materials have particular colors when no external electric field is applied and then their colors disappear in the presence of an electric field.
Electrochromic devices based on electrochromism offer the advantages such as high reflectance without the need for external light sources, flexibility, portability and are lightweight. Based on these advantages, electrochromic devices are expected to have many applications in various flat-panel displays. In particular, electrochromic devices have drawn considerable attention in recent years for their applicability to electronic paper, which is currently being investigated as an electronic medium for replacing traditional paper.
Such electrochromic materials are known to include, for example, inorganic compounds, such as, tungsten oxide and molybdenum oxide; and organic compounds, such as, pyridine compounds, aminoquinone compounds and azine compounds.
In comparison with inorganic electrochromic materials, organic electrochromic materials are disadvantageous in terms of long-term stability. However, organic electrochromic materials have advantages in that they are applicable to flexible substrates and can be used to form thin films by wet processes. Based on these advantages, a great deal of research has been conducted on organic electrochromic materials.
In order to achieve full-color electrochromic devices, a combination of red, green and blue are required. However, few red electrochromic materials are been known to date. Under such circumstances, there exists a strong need in the art to develop red electrochromic materials.